The present invention relates to a novel and unique remover solvent for partial removal of a photoresist layer on a substrate or, more particularly, to a remover solvent suitable for partial removal of a photoresist layer from the marginal areas, peripheral areas and/or back surface of a substrate prior to pattern-wise light exposure of the photoresist layer in the photolithographic patterning process for the manufacture of, for example, semiconductor devices such as ICs, LSIs and the like and liquid crystal display panels.
As is well known, a typical procedure of the above mentioned photolithographic patterning process in the manufacture of semiconductor devices is as follows. Namely, a substrate plate such as a semiconductor silicon wafer is coated on one surface with a photoresist composition in the form of a solution followed by drying to form a dried photoresist layer on the substrate surface. Subsequently, the photoresist layer is pattern-wise exposed to actinic rays to effect an increase or decrease in the solubility of the resist layer in a developer solution.
In the above mentioned coating step of the substrate surface with a photoresist solution, it is always the case that the photoresist solution is deposited not only onto the areas of the substrate surface intended for patterning, referred to as the patterning areas hereinafter, but also onto the areas not intended for patterning, referred to as the non-patterning areas hereinafter, such as marginal areas, peripheral areas and, sometimes, back surface of the substrate. Accordingly, it is very important that the photoresist layer formed on the non-patterning areas, referred to as the extraneous resist layer hereinafter, is removed, prior to the pattern-wise light exposure of the photoresist layer, by dissolving away with a remover solvent in order not to adversely affect the working efficiency in the subsequent processing steps.
A great variety of solvents are proposed and currently employed either singly or as a mixture of two kinds or more for use as the remover solvent. For example, propyleneglycol monomethyl ether acetate or a mixture thereof with propyleneglycol monomethyl ether is recommended and widely employed as a remover solvent in respect of the low toxicity to ensure excellent safety to the workers' health. When the remover solvent of this type is employed in the manufacture of a liquid crystal display panels by forming a photoresist layer on a glass substrate, drawbacks are sometimes encountered. For example, the remover solvent is absorbed in the photoresist layer on the patterning areas so that swelling of the photoresist layer left unremoved takes place along the boundary lines with the non-patterning area from which the extraneous photoresist layer has been removed by the remover solvent and consequently the periphery of the photoresist layer on the patterning areas cannot be orthogonal standing vertically on the substrate surface. Even worse, it is sometimes the case that the photoresist layer on the patterning areas is also partly dissolved away by the remover solvent.
With an object to overcome the above mentioned drawbacks in the use of conventional remover solvents, the inventors previously proposed use of an aqueous solution containing a basic compound and dipropyleneglycol mono(lower alkyl) ether as a remover solvent in Japanese Patent Kokai 9-269601 and 9-311470, respectively. Although these remover solvents are effective to solve the problems in the prior art remover solvents, it is desired in recent years to accomplish higher and higher productivity in the pre-exposure partial removal of the extraneous photoresist layer by decreasing the time taken for dissolving away the photoresist layer with a remover solvent. The inventors accordingly have continued investigations to develop a novel remover solvent of increased dissolving power leading to completion of the present invention.
The remover solvent as the target of the above mentioned development works must satisfy various requirements that partial removal of the photoresist layer in the non-patterning areas can be completed desirably within 6 seconds or shorter, that orthogonality is ensured of the periphery of the photoresist layer left unremoved on the patterning areas of the substrate surface, that the remover solvent is never absorbed in the photoresist layer left unremoved by the remover solvent, that no or little scums are formed after partial removal of the photoresist layer, that the remover solvent has good vaporizability not to prolongedly remain on the substrate surface so as to accelerate completion of the partial removal works, and so on.